1. Field of the Invention.
The present invention relates to a fixation device for immobilizing two portions of a bone at a joint, which may be a natural joint or a fracture.
2. Description of the Prior Art.
Various fixation devices for securing two segments of fractured bone, or for immobilizing a normal joint have been advanced.
The most common technique currently used for influencing fusion between two bone segments is to employ an external frame attached to pins that have points engaging the bone above and below the joint. The pins protrude through the skin and are fixed to clamps that can be compressed one against the other through the external device. The external fixation device is associated with a bulky external frame which may create problems with the opposite limb. In addition, complications of infection around the pins which protrude through the skin can be major problems. Internal fixation with screws across the joint is also used, but the screws do not allow for the bone segments to settle against each other as resorption of bone occurs and, therefore, may end up distracting the two bones as time goes on.
U.S. Pat. No. 3,986,504 shows an internal fixation device for securing two fractured bone joints together. This is a elongated probe having an outer sheath that is driven through the end of the bone that is broken (it appears that it has to be a large bone for use). After the sheath has been driven to span the break sufficiently a screw thread member that is on the interior of the outer sheath is actuated causing pins to be spread out to grip the bone, and the screw tends to pull the joint together.
Use of the device appears to cause excessive trauma, and because the location of the inserted part is dependent upon alignment of the sheath when it is initially pounded into the end of the bone, it would tend to be difficult to use.
Typical external fixation devices are sold by Howmedica, Inc. of Rutherford, N.J. Large external fixation frames sold under the trademark HOFFMANN are provided for the ankle and knee and other portions of the body. The frames are very awkward, because they are large, bulky, and tend to be bumped, and will catch on things if the patient is mobile. Additionally, the devices incorporate probes or pins that pass through the skin causing points of potential infection. The pins are difficult to fix tightly so that there is a tendency of the pins to slip when in use.
A device very similar to devices sold by Howmedica, Inc. is shown in U.S. Pat. No. 4,360,012. It comprises a large external frame that is placed on the outside of the body and forms a splint for fixing fractures. Another external fixation device is shown in U.S. Pat. No. 4,308,863. This patent also shows the typical use of external frames having transfixing pins that are positioned against the bone and pass through the skin and tissue to reach the bone. Again, the pins pass through the skin, which are locations susceptible to infection.
An articulated external fixation device is shown in U.S. Pat. No. 4,098,269 operating on the same principle except that the pins shown are actually screwed into the bony part to be immobilized. While this tends to hold the pins in place, the screw pins can irritate adjacent tissue and may come loose, and of course the pins still have to pass through the skin, which provides a scource of infection. Further, if the pins are not screwed in correctly, there is a chance of bumping the device and further damaging the bone where the pins enter the bone.
An internal fixation device for bone fractures is shown in U.S. Pat. No. 4,364,382. It is a metal plate that has edge fastening formations on two edges that will tend to secure the bone fracture site by deforming the plate so it penetrates into the bone and bridges the bone fracture. The plate fits over the bone, so that it is not within the bone, but it is beneath the skin.
Drilling and cutting bones with various devices has been known in the past as well. For example, U.S. Pat. No. 4,373,518 discloses a method of drilling live bone, and U.S. Pat. No. 4,416,278 illustrates a bone plug cutter that will permit cutting a plug of bone for implanting a prosthesis. Its primary use is in hip arthroplasty.
A prosthetic bone joint for hip reconstruction that is inserted into the bone canal or bore and which has means for centering it in the bore is shown in U.S. Pat. No. 3,793,650. This centering device is for insuring that the stem that goes into the bore is centered so that cement will surround the part and hold it securely.
A hip joint prosthesis is shown in U.S. Pat. No. 3,829,904, and this also utilizes a device with a stem that fits into the interior canal of a bone.
Various telescoping members have been advanced. For example telescoping tools and couplings are shown in U.S. Pat. No. 4,277,197, and a tool turret mechanism having telescoping parts is shown in U.S. Pat. No. 4,300,418. However, these devices are merely of general interest to show that telescoping members have been known, but have nothing to do with reconstruction of bone joints.